Author Topic: Magnetic propellant settling  (Read 3423 times)

Offline Nilof

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Magnetic propellant settling
« on: 08/02/2023 01:48 pm »
Liquid Oxygen is (para)magnetic. Could this be used to passively make propellant settle near the propellant inlets in zero g?
« Last Edit: 08/02/2023 01:50 pm by Nilof »
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Online edzieba

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Re: Magnetic propellant settling
« Reply #1 on: 08/02/2023 02:54 pm »
Gaseous oxygen is also paramagnetic, so that may not provide effective stratification for tanks using autogenous pressurisation.

Offline Twark_Main

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Re: Magnetic propellant settling
« Reply #2 on: 08/02/2023 06:59 pm »
I think that even in if the ullage gas is equally paramagnetic, stratification will still be achievable because 1 mL of LOX contains "more magnet" vs 1 mL of GOX, therefore stratification is energetically preferred.

This is of course easy to test experimentally: just put some LOX in a test tube with a vented cap (ensuring all the air inside gets replaced with GOX) and see if the LOX is still visibly attracted to a neodynium magnet.


A few selected links on the subject:

https://space.stackexchange.com/questions/14313/is-the-paramagnetism-of-liquid-oxygen-ever-considered-in-engine-or-tank-design

https://www.sciencedirect.com/science/article/pii/S0895717710000087

https://www.sciencedirect.com/science/article/abs/pii/S0094576521003428 (PDF here)

https://www.nature.com/articles/s41526-022-00212-9

https://www.sciencedirect.com/science/article/pii/S0094576522005495 (PDF here)
« Last Edit: 08/02/2023 07:02 pm by Twark_Main »

Offline Jim

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Re: Magnetic propellant settling
« Reply #3 on: 08/02/2023 10:20 pm »
don't see how this would be an advantage.  the complexity and power requirements outweigh a simple thruster system.

Offline Comga

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Re: Magnetic propellant settling
« Reply #4 on: 08/02/2023 11:09 pm »
don't see how this would be an advantage.  the complexity and power requirements outweigh a simple thruster system.
Even you cannot make such a blanket statement with confidence.
Plus it normalizes the complexity of “a simple thruster system” with its valves, and igniters and so on.  These are well developed, but not “simple”.
We are seeing many chemical and mechanical and hydraulic subsystems replaced by electronic and electromechanical ones, particularly as reusability and mission durations increase.
Not to say it’s preferred today.
It’s just too early to rule it out categorically. 
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline Jim

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Re: Magnetic propellant settling
« Reply #5 on: 08/02/2023 11:37 pm »

Even you cannot make such a blanket statement with confidence.
Plus it normalizes the complexity of “a simple thruster system” with its valves, and igniters and so on.  These are well developed, but not “simple”.
We are seeing many chemical and mechanical and hydraulic subsystems replaced by electronic and electromechanical ones, particularly as reusability and mission durations increase.
Not to say it’s preferred today.
It’s just too early to rule it out categorically. 

Yes, I can.  A "simple thruster system" is a cold gas sytems with two nozzles and one valve using a GN2 tank or even simpler tied into an existing pressurant tank.  This would use just only one signal line from the avionics system.  Also, the system is not totally parasitic, it adds to the stage delta V.  This is system settles all propellants and not just a magnetic ones (how would RP-1 be settled?).   If the propellants are cryogenic, then there is an "unlimited" source of gas for ullage management.

A magnetic system is going to need power and large? magnets to pull fluid through out the entire volume of a tank.   I bet just one battery or power system of the magnetic system is heavier than the cold gas system.  Also, electronics nearby would have to be shielded.
« Last Edit: 08/02/2023 11:40 pm by Jim »

Offline Twark_Main

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Re: Magnetic propellant settling
« Reply #6 on: 08/03/2023 02:04 am »
If anything is gonna "kill" paramagnetism for propellant management (PM), it's traditional surface tension PMDs.

https://en.wikipedia.org/wiki/Propellant_management_device
« Last Edit: 08/03/2023 02:09 am by Twark_Main »

Offline Nilof

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Re: Magnetic propellant settling
« Reply #7 on: 08/09/2023 02:01 pm »
Magnetism could be combined with surface tension, to make the oxygen more likely to stick to the surface in the first place.

As for thrusters, there are situations where you may not want to use them, like for example in propellant depots where you may want to be able to transfer propellant (slowly) without subjecting the docking connector to stress by accelerating two large spacecraft
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Online edzieba

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Re: Magnetic propellant settling
« Reply #8 on: 08/09/2023 03:40 pm »
Magnetism could be combined with surface tension, to make the oxygen more likely to stick to the surface in the first place.

As for thrusters, there are situations where you may not want to use them, like for example in propellant depots where you may want to be able to transfer propellant (slowly) without subjecting the docking connector to stress by accelerating two large spacecraft
I can think of few propellant transfer scenarios where settling thrust would not be desirable, and those involve bladdered tanks that would not require PMDs in the first place.

Offline Greg Hullender

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Re: Magnetic propellant settling
« Reply #9 on: 08/09/2023 04:04 pm »
So the plan is to use paramagnetism for the oxygen but use ullage thrusters for the methane? I think that might lead to the kind of separation you don't want!

Offline Jim

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Re: Magnetic propellant settling
« Reply #10 on: 08/09/2023 05:07 pm »
Magnetism could be combined with surface tension, to make the oxygen more likely to stick to the surface in the first place.

As for thrusters, there are situations where you may not want to use them, like for example in propellant depots where you may want to be able to transfer propellant (slowly) without subjecting the docking connector to stress by accelerating two large spacecraft
I can think of few propellant transfer scenarios where settling thrust would not be desirable, and those involve bladdered tanks that would not require PMDs in the first place.

Bladders are usually not use with cryogens

Online edzieba

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Re: Magnetic propellant settling
« Reply #11 on: 08/09/2023 07:58 pm »
Magnetism could be combined with surface tension, to make the oxygen more likely to stick to the surface in the first place.

As for thrusters, there are situations where you may not want to use them, like for example in propellant depots where you may want to be able to transfer propellant (slowly) without subjecting the docking connector to stress by accelerating two large spacecraft
I can think of few propellant transfer scenarios where settling thrust would not be desirable, and those involve bladdered tanks that would not require PMDs in the first place.

Bladders are usually not use with cryogens
Sure would make things easier if you could!
But that's why you'd want settling thrust for transfers without bladdered tanks - to maintain phase separation, and cryogens are going to be trying to produce separate phases all the tine you're handling them.

Offline TrevorMonty

Re: Magnetic propellant settling
« Reply #12 on: 08/09/2023 08:32 pm »
For fuel transfer still need thrust. Where magnetic settling couldchelp is reducing boiloff. Would concentrate liquid which should help compared to lot of droplets floating around in tank with their greater surface area.


Offline jongoff

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Re: Magnetic propellant settling
« Reply #13 on: 08/09/2023 11:11 pm »
Liquid Oxygen is (para)magnetic. Could this be used to passively make propellant settle near the propellant inlets in zero g?

Nilof,

Yeah, there's been some research on this concept. Dr Jeffrey Marchetta was one of the researchers you could google. You can definitely settle LOX with magnets -- heck I think I've seen pictures of people picking up globs of LOX in 1G with a strong enough NdFeB magnet. It's worth mentioning that Methane and LH2 are mildly diamagnetic, and with a strong enough magnet you can push them away. So yeah, magnetic propellant positioning is an idea that's had some research done on it. As Jim mentions, for rockets just using propulsive settling is simpler, but for very long duration storage, something like MPP could trade better.

Here's a few links to papers on Researchgate:
https://www.researchgate.net/publication/239609646_Modeling_and_Prediction_of_Magnetic_Storage_and_Reorientation_of_LOX_in_Reduced_Gravity
https://www.researchgate.net/publication/225402321_Simulation_of_LOX_reorientation_using_magnetic_positive_positioning
https://www.researchgate.net/publication/223267421_Simulating_magnetic_positive_positioning_of_cryogenic_propellants_in_a_transient_acceleration_field
https://www.researchgate.net/publication/364320111_Novel_propellant_settling_strategies_for_liquid_rocket_engine_restart_in_microgravity
https://www.researchgate.net/publication/338832214_Prospects_and_Challenges_for_Magnetic_Propellant_Positioning_in_Low-Gravity

~Jon
« Last Edit: 08/10/2023 12:41 am by jongoff »

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